The mineralized tissue of the bones of the human skeletal system are generally categorized into two morphological groups: “cortical” bone and “cancellous” bone. The outer walls of all bones are composed of cortical or “compact” bone. Cortical bone is characterized by a dense structure with only microscopic porosity. In contrast to cancellous bone, cortical bone tissue is much harder and denser. Cortical bone provides a protective layer and support for bones such as vertebral bodies. Cancellous or “trabecular” bone is found in the interior of bones. This tissue is composed of an interconnected framework and reinforcement called “trabeculae.” Physicians have developed methodologies to treat bones by accessing their interior structure using a percutaneous approach. For example, they have artificially replenished the space left where trabeculae are lost due to collapse and/or compression of vertebral bodies.
These types of treatments are critical when a vertebral body collapses, commonly know as a compression fracture. Such injuries are often noted in individuals with osteoporosis or osteopenia as well as other diseases such as myeloma, a form of bone cancer. Osteoporosis is a disease of the bone that is most commonly found in the middle-aged and the elderly, particularly women. It is characterized by a gradual loss or demineralization of spongy cancellous bone, causing the remaining bone to become brittle and lose elasticity, thus rendering the bone weaker and more prone to fracture. Where osteoporosis has significantly weakened the cancellous bone, the cortical bone may be similarly affected and/or unable to solely support the loads placed on the spine, and thus the vertebral bodies become especially prone to fracture.
Vertebroplasty and Kyphoplasty are two minimally-invasive procedures that have been developed to access and treat diseased or fractured bone, such as collapsed or fractured vertebral bodies in individuals suffering from osteoporosis. These procedures require a bilateral approach into vertebral structures. In a vertebroplasty procedure, after the interior bone is accessed, poly-methylmethacrylate (PMMA) or bone cement is injected directly into the interior of a weakened and/or fractured bone in an attempt to reinforce the bone and prevent further weakening or fracture. In a Kyphoplasty procedure, a surgeon similarly accesses the interior of the bone with a bilateral approach. The surgeon then uses additional techniques and surgical tools to compact the cancellous bone and expand the cortical bone of the weakened and/or fractured vertebral body. Then the surgeon introduces a filler material such as bone cement into the bone. This procedure may prevent further fracture or subsidence of the bone.
Both of these procedures seek to alleviate the pain and discomfort experienced by patients suffering from vertebral compression fractures, and both procedures seek to reinforce a fractured and/or weakened vertebral body against further fracture. Both procedures include protocols for introducing filler material to form an “internal cast” to support the vertebral body against further overload.
Both of these techniques are invasive, but are considered minimally-invasive. The procedures employ an access tool or similar portal system such as a straight, rigid cannula having an interior lumen through which the interior of the bone is accessed. These access tools, which are typically designed to penetrate rigid tissue such as cortical bone, generally require significant column strength to penetrate and transit the rigid tissue and are thus essentially non-expandable. Consequently, the size of the inner lumen of such access tools basically defines the maximum dimensions of any therapeutic substance and/or surgical tool that can pass through the access tool into the vertebral body.
Because a vertebroplasty procedure does not currently call for the insertion of tools through the cannula and only calls for the injection of a flowable material such as bone cement into the fractured vertebral body, the lumen of the access tool necessary for introduction of such substances can be rather small. A common access tool used in a vertebroplasty procedure is an 11-gage spinal needle having an outer diameter of 0.120 inches and an interior lumen approximately 0.095 inches in diameter. Because the access tool for a vertebroplasty is of such small diameter, very little soft tissue and/or bone trauma is caused. The smaller access path allows the tool to be inserted through the pedicles in the vertebral bodies of the thoracic and lumbar regions of the human spine. The disadvantage of vertebroplasty is that surgeons are not able to affect change in the cancellous bone. Furthermore, the simple injection of filler necessitates use of higher pressures which can cause damage or an uncontrollable leakage of cement to a non-targeted, vital structure such as a nerve or blood vessel.
In contrast, a Kyphoplasty procedure employs tools, such as inflatable bone tamps, to compact the cancellous bone and move the cortical bone in an attempt to restore the vertebral body. These tools generally require a larger access path than that required for a typical vertebroplasty procedure. An access tool suitable for use in a Kyphoplasty procedure is approximately four times larger than a cannula used for vertebroplasty. Such larger tools, however, can potentially cause additional soft tissue and bone damage and may be unsuitable for insertion through smaller access paths, such as through the pedicles in the vertebral bodies of the thoracic and lumbar regions of the human spine.
A Kyphoplasty procedure has advantages over a vertebroplasty procedure; however, the tools that currently exist for creating a void within the bone have not been fully adapted to meet the needs of patients. The existing Kyphoplasty void-creation devices rely on a great degree of chance for preparing the bone. A surgeon does not have the control desired to designate the size and shape of the void created. Furthermore, the current tools do not provide sufficient strength to exert the needed force to affect vertebral bodies, particularly where a patient has suffered a fracture that is aged and partially healed.
The Kyphoplasty procedure can be described as follows: (1) insertion of a straight, sharp obturator and straight cannula assembly into the pedicle; (2) withdrawal of the blunt obturator leaving the cannula in place; (3) insertion of a drill, drill a channel, and withdraw of the drill; (4) insertion of an expandable structure (such as a balloon), expansion and contraction of the structure and then removal of the structure leaving a void; and (5) filling the void with cement or other substrate. The current Kyphoplasty protocols fail to allow control, which practitioners demand, over the void creation parameters.
In an effort to solve these problems, other inventions have sought to provide a transpedicular approach into the bone and then attempt to perpendicularly articulate after entering the interior bone. Such inventions have a number of unfavorable outcomes. First, inventions using a hinge to achieve articulation cannot be engaged because there is insufficient space to allow for the tool to articulate inside the bone. Many such inventions do not have a locking mechanism to allow partial articulation so that sufficient space for full engagement may be created. These supposed cavity creating tools only result in a tamping mechanism useful in extension of the cannula. The limited strength and space for articulation restrict these inventions from reaching an operational position. The current tools in the art do not contemplate a necessary curved configuration coupled with a fixed tip to effectuate the optimum result.
A need exists for a tool which can function in either a vertebroplasty, Kyphoplasty, or similar internal-bone treatment procedure, which will pass through a cannula or bone access tool and also allow immediate impact in axial or lateral directions. In order to optimize surgical procedures, an extrapedicular approach into the bone is needed. An ideal tool would create a critical curve gradient for approaching the bone in a unilateral manner.
A further need exists for a tool with sufficient tensile strength to allow a surgeon to freely prepare bone tissues for treatment. Prior inventions have sought to provide extraordinary safety features which would prevent injury to a patient if the tool became dislodged. The result has produced over-engineered products that do not leave enough strength on the distal end to provide a tool that is strong enough to perform the desired function of preparing the bone for treatment. There is a need in the industry for a tool which possesses the strength to effectively prepare the bone tissue while retaining some flexibility and protecting a patient's health.
These disadvantages and shortcomings of the prior art are presented for the reader's understanding only. This disclosure is not meant to limit the present invention in any way. Other features and advantages of the present invention are set forth and will become apparent in the following description and drawings, as well as in the appended claims.